A method for uncovering coal in high-gassy and low-permeability coal seams by phase transition fracturing of liquid carbon dioxide

Abstract

The invention discloses a high-gas hypotonic coal bed liquid carbon dioxide phase change fracturing rock cross-cut coal uncovering method. The method comprises the following steps that 1, look-ahead geological drilling is carried out; 2, liquid carbon dioxide phase change fracturing hole and gas extraction hole construction is carried out; 3, liquid carbon dioxide phase change fracturing anti-reflection gas extraction is carried out; 4, gas extraction effect testing is carried out; 5, liquid carbon dioxide phase change fracturing exploding coal uncovering is carried out; 6, mucking and cleaning are carried out, and the machine enters a coal bed. The liquid carbon dioxide phase change fracturing technology is adopted, fracturing anti-reflection operation is carried out on coal uncovering area coal bed gas, and the gas permeability coefficient of the coal bed gas is increased; on the basis of the fracturing radius determined through field tests, the extraction drilling clearance can be properly increased, the drilling engineering amount can be effectively reduced, high-concentration extraction of the coal bed gas and fast elimination outburst of a coal uncovering area hypotonic high-gas coal bed can be achieved, the aim of preventing rock cross-cut coal uncovering from inducing coal and gas outburst is achieved, the investment cost is low, and the gas extraction effect is good.

Description

technical field [0001] The invention relates to a method for uncovering coal in Shimen. Background technique [0002] Shimen is a horizontal roadway that is not directly connected to the ground, and its long axis is perpendicular to or obliquely intersected with the coal seam. The main roadway into the coal seam. Shimen unraveling refers to the process of coal mine tunneling through the rocky roadway and entering the coal roadway. The Shimen tunneling face starts from the minimum normal distance of 10m from the bottom (top) slab of the outburst coal seam until it passes through the coal seam and enters the top (bottom) slab 2m. (Minimum normal distance) process belongs to uncovering coal operation. Before the coal seam is exposed, the coal body is sealed by the surrounding rocks of the roof and floor, and is in the stress concentration area, the elastic potential and gas internal energy in the coal seam cannot be released, and coal and gas outbursts are very likely to occu...

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Problems solved by technology

[0003] During the specific coal uncovering operation process, due to the limited effect of a single outburst prevention measure, the progress of the Shimen coal uncovering project is slow, which affects the normal production of the coal mine; and unreasonable coal uncovering methods may cause artificial induction during the coal uncovering process. Protrusion, etc., are extremely unfavorable to coal mine safety production

[0004] In the prior art, the method of adopting hydraulic fracturing to unearth coal in Shimen has appeared, but the hydraulic fracturing method has the following disadvantages: 1. Due to the complex geological conditions of coal seam occurrence, the hydraulic fracturing anti-permeability method cannot guarantee the performance of fracturing. Uniform fractures are generated in the area, so in the process of field application, there are often cases where fracturing in some areas is not in place, and the effect of coal seam gas drainage is not good, which affects the coal uncovering work to a certain extent

2. Hydraulic fracturing requires the injection of a large amount of high-pressure water inside the coal seam. On the one hand, the increase in the water content of the coal seam fractures will affect the analysis of the adsorbed gas in the coal seam. On the other hand, the water injected into the coal body will seep from the coal seam Cause water in the working area of ​​roadway excavation, and worsen working conditions; 3. Hydraulic fracturing anti-reflection requires a large plunger high-pressure water pump in the coal mine, and the economic cost is high

5. The coal seam water injection is used to freeze and expand, because the water will only flow along the coal seam cracks, so the cracking effect is uneven, which will cause poor permeability enhancement effect in some areas of the coal seam

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